Skip washing the head if one is suffering a severe headache

Q. When taking an obligatory bath (ghusal), can we skip washing our heads if we are suffering a severe headache?

A. If cold water causes a terrible headache, then we must use hot water. In case the latter is also harmful, then it is permissible to do "masah", i.e. to pass wet hands over the head. This "masah" will be valid as long as we cannot use cold or hot water. However, as soon as one feels better or can use cold or hot water, it will be obligatory to wash one's head. For example, if one cannot wash with cold or hot water in the morning, but in the afternoon it is possible, then the masah will be valid for the morning only. This means that in the afternoon it will be obligatory to wash one's head because the "masah" will not be valid at that time. It is good to specify here that it is sufficient in this case to wash ONLY one's head to complete the bath (ghusal).

[English version of "Se passer du lavage de la tête lorsqu'on en souffre atrocement" – Al Haadi – Vol. 1 No. 7]